The objective of this study was to analyse retrieved human femoral bone samples using three different test
methods, to elucidate the relationship between bone mineral density and mechanical properties. Human femoral heads
were retrieved from 22 donors undergoing primary total hip replacement due to hip osteoarthritis and stored for a
maximum of 24 hours postoperatively at + 6 °C to 8 °C.Analysis revealed an average structural modulus of 232±130 N/mm2 and ultimate compression strength of 6.1±3.3 N/mm2 with high standard deviations. Bone mineral densities of 385±133 mg/cm2 and 353±172 mg/cm3 were measured using thedual energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT), respectively. Ashing resulted in a bone mineral density of 323±97 mg/cm3. In particular, significant linear correlations were found between DXA and ashing with r = 0.89 (p < 0.01, n = 22) and between structural modulus and ashing with r = 0.76 (p < 0.01, n = 22).Thus, we demonstrated a significant relationship between mechanical properties and bone density. The correlations found can help to determine the mechanical load capacity of individual patients undergoing surgical treatments by means of noninvasive bone density measurements.
The bone mineral density (BMD) of retrieved cancellous bone samples is compared to the BMD measured in vivo in the respective osteoarthritic patients. Furthermore, mechanical properties, in terms of structural modulus (E
s) and ultimate compression strength (σ
max) of the bone samples, are correlated to BMD data. Human femoral heads were retrieved from 13 osteoarthritic patients undergoing total hip replacement. Subsequently, the BMD of each bone sample was analysed using dual energy X-ray absorptiometry (DXA) as well as ashing. Furthermore, BMDs of the proximal femur were analysed preoperatively in the respective patients by DXA. BMDs of the femoral neck and head showed a wide variation, from 1016 ± 166 mg/cm2 to 1376 ± 404 mg/cm2. BMDs of the bone samples measured by DXA and ashing yielded values of 315 ± 199 mg/cm2 and 347 ± 113 mg/cm3, respectively. E
s and σ
max amounted to 232 ± 151 N/mm2 and 6.4 ± 3.7 N/mm2. Significant correlation was found between the DXA and ashing data on the bone samples and the DXA data from the patients at the femoral head (r = 0.85 and 0.79, resp.). E
s correlated significantly with BMD in the patients and bone samples as well as the ashing data (r = 0.79, r = 0.82, and r = 0.8, resp.).
This study focuses on understanding the influence of extreme environmental conditions on silicone oil applied as an insulating material in underwater electrical switching systems. The extreme environmental conditions imply adverse operating temperatures of the underwater electrical systems which must be effectively handled by the silicone oil. For this purpose, a standard high voltage (HV) relay is selected and is immersed in a silicone oil thereby enhancing its operating voltage to 20 kV. First, the geometry of the modified relay switch is captured and converted into a CAD model. Subsequently, the developed CAD model is imported into the simulation software and converted into a numerical model and subjected to AC/DC, electrostatic and stationary case simulation. The adverse temperature conditions are varied i.e., from −50 °C, 0 °C, 20 °C, 40 °C and 120 °C respectively. The potential and electric field displacement at the electrodes of the high voltage relay is recorded and analyzed. Following this, high voltage experiments are carried out on an actual high voltage relay constructed based on the simulation model and the respective parameters such as discharges. Thus, the dielectric quality of the silicone oil under wide range of temperature is studied. The simulation and experimental results obtained altogether validate the design modifications made on the standard relay converted to meet the high voltage requirements of underwater electrical switching systems.
Once this is identified, the chosen relay is compared with the experimental findings to validate the design modification.
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